Constant voltage float charge rectifier and battery surveillance apparatus is generally employed in installations where a DC operating load is constantly in operation, drawing EI regulated DC from a float charge rectifier, whose output is also connected to a battery in parallel with the load. Thus, in the event of failure of the AC input to the apparatus, the battery carries the load and continues to provide it with electrical energy, until such time as the supply of alternating current power to the apparatus is re-initiated. Such installations include remote installations where power is being provided for satellite transmission stations, pipeline surveillance apparatus, military or other high security installations; and, as well, in operations such as general telephone exchanges, computer installations and the like.
However, in all such installations, there are several requirements that are constant to such installations, and very often there are additional user-determined requirements that may also be necessary for the operation of the float charge rectifier and battery surveillance apparatus. These include such matters as maintaining a constant, full-time battery and circuit operation surveillance, including an indication as to the continuing supply of energy from the alternating current electrical energy source, and an indication as to whether the apparatus is at any instant of time in a constant voltage float charge mode or in a battery re-charging and equalization mode of operation.
Moreover, the apparatus may generally be required to provide an indication of battery low voltage, or of a general failure of the apparatus. Further, it is sometimes desireable that such indications or signals indicative of the presently existing operation status and/or alarm status should be transmitted to a remote alarm indicating station.
However, such apparatus has, in the past, generally comprised operating systems that are a combination of individually operating components, which are very often interfaced in such a manner that regulation is difficult and energy losses are significant.
Still further, it is desireable that there be a provision that there should be no current drain from the battery to the apparatus, except for the maintenance of system status indication circuits, during any outage of the AC source. Moreover, it is desireable, especially when two or more systems are in operation and connected to the same source of alternating current electrical energy, that there should be "soft" walk-in, or even a soft staggered walk-in, so as to preclude overloading the AC source. However, such requirements have not been well met previously, due to the hard connection of such float charge rectifier apparatus to the AC input source through fused safety disconnects or circuit breakers, except by the addition of extra electronic and/or magnetic circuit controllers.
It is particularly desireable that a battery re-charging and equalization program be initiated after any failure of the alternating current energy supply for more than a predetermined period of time, usually five minutes. Moreover, so as to maintain the battery in peak operating condition and efficiency, it is desireable in any event, and even when there has been no failure of the AC energy supply, that the battery be subjected to a re-charging and equalization program periodically. The length of such period has normally been determined to be 30 days but it may be longer or shorter.
Still further, it is desireable that a battery re-charging and equalization program should be initiated in the event that there has been deep discharge of the battery, even if there has not been an AC outage.
Generally, the period for battery re-charging and equalization is 8 to 12 hours, but depending upon the type of installation and circumstances surrounding it, it is desireable that the apparatus be adjustable to provide for a battery re-charging and equalization program of up to, say, twenty-four hours.
Finally, it is desireable, in all events, that the battery re-charging and equalization program be a substantially constant voltage program at a voltage which is higher than the normal float charge voltage for the battery.
Whether the electrical load connected to the constant voltage float charge rectifier and battery surveillance apparatus of the present invention is capable of operating at the higher re-charging and equalization voltage level as well as at the general float charge voltage level is essentially immaterial. Counter-EMF cells may be provided, or optional switching or other circuit means, whereby the load is protected from higher voltage in the event that it is necessary.
In any event, all of the above desireable features are provided, together with others, by the apparatus of the present invention, in a fully integrated operating circuit, to which may be added other circuit means which provide additional functions as may be required or desired, from time to time, and from installation to installation, depending upon the user's specific demands. For example, means are provided to manually initiate an equalization program at any time, and means may be provided to give an alarm indication upon sensing a battery low voltage, or means may even be provided to shut down the apparatus in the most unlikely event of circuit operation whereby the voltage output from the apparatus might increase beyond a predetermined level.
The present inventor has provided several circuits and apparatus for battery charging, in the past, including one having an initial constant, high current output, which then transfers to a taper (constant voltage) output, and finally to a trickle (constant current) charge. That battery charger is described in detail in Hase, U.S. Pat. No. 3,848,173, issued Nov. 12, 1974.
A further battery charger circuit, having full-time surveillance, is described in detail in U.S. Pat. No. 4,320,333, issued Mar. 16, 1982, to Alfred M. Hase.
As noted, the above patents relate to battery charging apparatus per se, having constant current, then constant voltage, then constant current output; whereas the present apparatus relates more particularly, in the battery charging and float charging modes, to constant voltage charging operation at a higher or lower voltage level, respectively.
However, the present invention also specifically provides an apparatus which has regard to energy efficient solid devices and transformers, with a view to energy saving and particularly to preclude unnecessary power losses during low load conditions or during AC outages, whereby better regulation may also be provided.
The above are broadly stated descriptions of certain of the features and functions of the apparatus of the present invention, discussed in greater detail hereafter.
In general terms, however, the present invention at least provides a current limiting, two level constant voltage float charge rectifier and battery surveillance apparatus which has full-time battery and circuit operation surveillance, and which is adapted for connection at its input to a source of alternating current electrical energy and at its output to an electrical load parallel with a storage battery, whereby the apparatus supplies electrical energy to the load when the source of electrical energy is connected and provides a constant voltage float charging to the battery at a first voltage level, and provides a battery re-charging and equalization program at a second voltage level which is higher than the first voltage level. The apparatus, in all events, comprises controllable synchronous switch means--discussed in greater detail hereafter--having a control coil, for controlling the rate of electrical energy input to the load which is in parallel with the storage battery, to which the apparatus is connected. The constant voltage float charging and constant voltage electrical energy input to the load, at the first voltage level, are continuous except when the apparatus is otherwise under control of a first, adjustable timing circuit. That adjustable timing circuit is adapted for setting a predetermined period of time and for controlling the battery re-charging and equalization program at a second voltage level which is higher than the first voltage level, during that predetermined period of time; and to automatically return to the constant voltage float charging and electrical energy supply program at the end of that predetermined period of time.
The apparatus further comprises adjustable fail-safe voltage sensing means; regulated fail-safe current limit sensing means; timer control cut-off means; and a general failure alarm circuit for detecting at least failure of the apparatus or of the source of electrical energy to the apparatus, and for generating a signal upon such failure. The regulated fail-safe current limit sensing means includes a zener diode in series with a diode and a potentiometer. The timer control cut-off means is such as to initiate a battery re-charging and equalization program so as to equalize the operating and sensed parameters of the apparatus following a predetermined delay after disconnection of the apparatus from the source of alternating current electrical energy, or failure of that source. Finally, in a minimum system according to the present invention, the adjustable fail-safe voltage sensing means drives shunt regulator means in parallel to the control coil of the controllable synchronous switch, so that the shunt regulator means drives the control coil by controlling the operating period thereof.
Other additional and/or optional features and operating sub-systems of the apparatus according to this invention, as well as the principles of operation, are set out hereafter.